Well, there’s only one.
It’s from physics, and its value shows how strong the interaction is for electromagnetic stuff.
It’s equal to about 1/137, almost exactly. There’s a formula for it in terms of various physical constants, but it won’t mean much unless you investigate what each of those constants is and does.
It measures the strength of ‘one charged particle absorbs, or emits, one photon’. MUCH MUCH stronger than gravity; weaker than the strong nuclear force.
–Dave, emitting an answer
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